This invention relates generally to bipolar electrosurgical instruments used in arthroscopic surgery for, e.g., cutting tissue, smoothing cartilage, and coagulating bleeding vessels or tissue.
It is well known to use monopolar surgical instruments in arthroscopy for cutting, smoothing, and coagulating. A monopolar instrument includes a single electrode to which radio frequency energy is applied. The patient is securely grounded (e.g., using a ground plate) so that current flows from the tip of the electrode into the target tissue and then randomly through the patient's body to ground. To coagulate, the tip of the electrode is placed in direct contact with the bleeding vessel.
When the instrument is used for cutting, a gap is maintained by the surgeon between the electrode tip and the tissue to provide space for the generation of an electric spark necessary to produce enough heat for efficient cutting. This heat penetrates the tissue surface and creates the cut. To prevent dissipation of the high electrical energy needed to produce sparking, a nonconductive fluid such as distilled water is used in the wound in place of electrically conductive, physiologic saline solution.
Reimels, U.S. Pat. No. 4,548,207, describes a bipolar electrosurgical instrument for coagulation of blood vessels and/or tissue in the form of a probe which includes coaxial inner and outer electrodes. Radio frequency power is applied across the bipolar electrodes of the instrument, and localized coagulation is performed by placing the tip of the instrument in contact with tissue. Conductive fluids such as saline can be used with this instrument because current flows only through tissue located adjacent the electrodes.